An O2 sensor is in general installed in the oil and air inlet ends or the exhausting tubes of the engines of cars and motorcycles for detecting the air to fuel ratios of the oil and air inlet ends or the oxygen contained in the waste gas exhausting ends. In other words, oxygen density in the gas (oil or wasted gas) to be measured is detected by the O2 sensor so as to supply control signals to the engine control unit to adjust the air to fuel ratio to an optimum value. Thereby, the exhaustion of harmful material in the air can be reduced.
It is appreciated that the conventional O2 sensor can be classified into a heating sensor and a non-heating sensor. The difference between the two is whether a thermal coupler is added in the sensor. The heating O2 sensor causes the electrode carriers in solid electrolyte materials to be heated rapidly to a temperature over 350° C. so that the O2 sensor can detect the air to fuel ratio or the potential signals of the sensor. On the contrary, the non-heating O2 sensor heats the electrode carriers by heat from the oil gas or wasted gas. Thereby, the reaction for sensing the potential signal is slow, but it can achieve a normal detection ability when the engine is actuated for a time period.
Moreover, the heating or non-heating O2 sensor must be added with a solid electrolytic electrode isolating carrier. Conventionally, the electrode isolating carrier is made of zirconium oxide (ZrO2). The conventional sensor is a solid electrolytic high temperature O2 sensor which is made of a single long strip-like electrode carrier. A channel communicated to an external atmosphere is formed within the carrier and the carrier is formed with a positive lead and a negative lead. The positive interface is in contact with the atmosphere through the channel and the negative interface is in contact with the waste gas. The positive interface and negative interface are chemically reacted with the solid electrolytic zirconium oxide carrier so as to decompose the oxygen in the atmosphere and gas to be measured to generate a voltage. The voltage is transferred through a single zirconium oxide carrier so as to detect the oxygen density of the gas to be measured or the air to fuel ratio.
However, it is known that in the whole carrier, only the peripheries of the positive interface and negative interface are necessary to generate the voltage by using the zirconium oxide. Other voltage transferring portions of the carrier are unnecessary to use zirconium oxide as a solid electrolyte. Furthermore, since the price of zirconium oxide is very expensive; and the electrode carrier in the conventional O2 sensor uses zirconium oxide as a solid electrolyte, the price of the sensor is high and the cost can not be reduced.